docs: def split_window(self, attach=False, vertical=True, start_directory=None):
          """
          Split window at pane and return newly created :class:`Pane`.
  
          Parameters
          ----------
          attach : bool, optional
              Attach / select pane after creation.
          vertical : bool, optional
              split vertically
          start_directory : str, optional
              specifies the working directory in which the new pane is created.
  
          Returns
          -------
          :class:`Pane`
          """
          return self.window.split_window(
              target=self.get('pane_id'),
              start_directory=start_directory,
              attach=attach,
              vertical=vertical,
          )